Sunday, March 29, 2015

Tsunami Warning Issued after M7.7 Earthquake - Papua New Guinea

29.03.2015

The USGS has since downgraded the event to M7.5
TSUNAMI THREAT FORECAST...UPDATED
---------------------------------
*THE TSUNAMI THREAT HAS NOW LARGELY PASSED.

The U.S. Geological Survey says a magnitude 7.7 #earthquake has struck in Papua New Guinea. The earthquake prompted a #tsunami warning.The USGS says the quake’s epicenter was located 33 miles (54 kilometers) southeast of Kokopo, Papua New Guinea and was at a depth of 65 kilometers. The quake hit at 3:48 p.m. PST Sunday.A tsunami alert was issued for coastal areas within 1,000 kilometers of the quake’s epicenter. There was no threat for the California coast.A tsunami alert was issued for coastal areas within 1,000 kilometers of the quake’s epicenter. There was no threat for the California coast.The USGS says the quake’s epicenter was located 33 miles (54 kilometers) southeast of Kokopo, Papua New Guinea and was at a depth of 65 kilometers. The quake hit at 3:48 p.m. PST Sunday.A tsunami alert was issued for coastal areas within 1,000 kilometers of the quake’s epicenter. There was no threat for the California coast.A tsunami alert was issued for coastal areas within 1,000 kilometers of the quake’s epicenter. There was no threat for the California coast.

A USGS map of an earthquake that hit M7.7 Earthquake (downgraded to M7.5) - Papua New Guinea. (Source: USGS)

Tectonic Summary

The March 29, 2015 M 7.5 earthquake southeast of Kokopo, Papua New Guinea, occurred as the result of thrust faulting on or near the plate boundary interface between the subducting Australia and overriding Pacific plates. At the location of the earthquake, the Australia plate moves towards the east-northeast at a velocity of 105 mm/yr with respect to the Pacific plate, and begins its subduction into the mantle beneath New Britain and New Ireland at the New Britain Trench south of the earthquake. The moment tensor and depth of the event are consistent with thrust-type motion on the interface between these two plates. Note that at the location of the earthquake, some researchers divide the edges of the Australia and Pacific plates into several microplates that take up the overall convergence between Australia and the Pacific, including the Solomon Sea and South Bismark microplates local to this event. The Solomon Sea plate moves slightly faster and more northeasterly with respect to the Pacific plate than does Australia due to sea-floor spreading in the Woodlark Basin several hundred kilometers to the south of the March 29 earthquake, facilitating the classic subduction evident beneath New Britain and New Ireland.

The plate boundary between the Australia and Pacific plates in the Papua New Guinea region is very active seismically; 36 M 7+ events have occurred within 250 km of the March 29, 2015 earthquake over the past century. Few are known to have caused shaking-related fatalities because of the remoteness of the region, though a M 8.0 earthquake in November 2000 – one of three similarly sized events over a 2-day period – did cause several deaths. The largest nearby earthquake was an M 8.1 event, 70 km to the east of the March 29, 2015 earthquake, one of two M8+ earthquakes 140 km apart in July 1971.

TSUNAMI MESSAGE NUMBER 4
NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
0230 UTC MON MAR 30 2015
...PTWC FINAL TSUNAMI THREAT MESSAGE...
**** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE *****
THIS MESSAGE IS ISSUED FOR INFORMATION ONLY IN SUPPORT OF THE
UNESCO/IOC PACIFIC TSUNAMI WARNING AND MITIGATION SYSTEM AND IS
MEANT FOR NATIONAL AUTHORITIES IN EACH COUNTRY OF THAT SYSTEM.
NATIONAL AUTHORITIES WILL DETERMINE THE APPROPRIATE LEVEL OF
ALERT FOR EACH COUNTRY AND MAY ISSUE ADDITIONAL OR MORE REFINED
INFORMATION.
**** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE *****
PRELIMINARY EARTHQUAKE PARAMETERS
---------------------------------
* MAGNITUDE 7.6
* ORIGIN TIME 2349 UTC MAR 29 2015
* COORDINATES 4.7 SOUTH 152.7 EAST
* DEPTH 33 KM / 20 MILES
* LOCATION NEW IRELAND REGION PAPUA NEW GUINEA
EVALUATION
----------
* AN EARTHQUAKE WITH A PRELIMINARY MAGNITUDE OF 7.6 OCCURRED IN
THE NEW IRELAND REGION, PAPUA NEW GUINEA AT 2349 UTC ON SUNDAY
MARCH 29 2015.
* BASED ON ALL DATA AVAILABLE TO THIS CENTER... THE TSUNAMI
THREAT FROM THIS EARTHQUAKE HAS NOW MOSTLY PASSED. ANY
REMAINING THREAT SHOULD BE EVALUATED BY LOCAL AUTHORITIES IN
IMPACTED AREAS.
TSUNAMI THREAT FORECAST...UPDATED
---------------------------------
* THE TSUNAMI THREAT HAS NOW LARGELY PASSED.
RECOMMENDED ACTIONS
-------------------
* GOVERNMENT AGENCIES RESPONSIBLE FOR ANY IMPACTED COASTAL
AREAS SHOULD MONITOR CONDITIONS AT THE COAST TO DETERMINE IF
AND WHEN IT IS SAFE TO RESUME NORMAL ACTIVITIES.
* PERSONS LOCATED NEAR IMPACTED COASTAL AREAS SHOULD STAY ALERT
FOR INFORMATION AND FOLLOW INSTRUCTIONS FROM LOCAL
AUTHORITIES.
* REMAIN OBSERVANT AND EXERCISE NORMAL CAUTION NEAR THE SEA.
POTENTIAL IMPACTS
-----------------
* MINOR SEA LEVEL FLUCTUATIONS OF UP TO 0.3 METERS ABOVE AND
BELOW THE NORMAL TIDE MAY CONTINUE OVER THE NEXT FEW HOURS.
TSUNAMI OBSERVATIONS
--------------------
* THE FOLLOWING ARE TSUNAMI WAVE OBSERVATIONS FROM COASTAL
AND/OR DEEP-OCEAN SEA LEVEL GAUGES AT THE INDICATED LOCATIONS.
THE MAXIMUM TSUNAMI HEIGHT IS MEASURED WITH RESPECT TO THE
NORMAL TIDE LEVEL.
GAUGE TIME OF MAXIMUM WAVE
COORDINATES MEASURE TSUNAMI PERIOD
GAUGE LOCATION LAT LON (UTC) HEIGHT (MIN)
-------------------------------------------------------------
TAREKUKURE WHARF SB 6.7S 156.4E 0159 0.03M/ 0.1FT 32
NOTE TIDE GAUGE AT TAREKUKURE WHARF IS 450 KM FROM THE EPICENTER.
NEXT UPDATE AND ADDITIONAL INFORMATION
--------------------------------------
* THIS WILL BE THE FINAL STATEMENT ISSUED FOR THIS EVENT UNLESS
NEW INFORMATION IS RECEIVED OR THE SITUATION CHANGES.
* AUTHORITATIVE INFORMATION ABOUT THE EARTHQUAKE FROM THE U.S.
GEOLOGICAL SURVEY CAN BE FOUND ON THE INTERNET AT
EARTHQUAKE.USGS.GOV/EARTHQUAKES -ALL LOWER CASE-.
* FURTHER INFORMATION ABOUT THIS EVENT MAY BE FOUND AT
PTWC.WEATHER.GOV AND AT WWW.TSUNAMI.GOV.
* COASTAL REGIONS OF HAWAII... AMERICAN SAMOA... GUAM... AND
CNMI SHOULD REFER TO PACIFIC TSUNAMI WARNING CENTER MESSAGES
SPECIFICALLY FOR THOSE PLACES THAT CAN BE FOUND AT
PTWC.WEATHER.GOV.
* COASTAL REGIONS OF CALIFORNIA... OREGON... WASHINGTON...
BRITISH COLUMBIA AND ALASKA SHOULD ONLY REFER TO U.S. NATIONAL
TSUNAMI WARNING CENTER MESSAGES THAT CAN BE FOUND AT
NTWC.ARH.NOAA.GOV.

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